Light transmission properties of electrochromic films or glasses change with the application of a voltage. The electrochromic material changes from a transparent state to a colored opaque or translucent state. Electrochromic devices are used in a variety of applications. One example of such electrochromic devices are electrochromic smart windows that are used to control the amount of light and heat allowed to pass through. Smart windows can save costs of heating and air-conditioning and provide adjustable lighting. Electrochromic smart windows can be used between rooms to provide walls with different states of light transmission. Electrochromic materials have also been used to tint rear-view mirrors in automobiles and to protect displays under glass in museum cases and picture frames from the damaging effects of ultra-violet and visible light.
Electrodes for applying a voltage are a necessary aspect of electrochromic devices. Current electrochromic materials suffer damage at temperatures above about 420° C. The electrodes must therefore be formed at temperatures below 420° C. There is an on-going need to provide thick film paste compositions that can be fired at temperatures below 420° C. while maintaining electrical performance and other relevant properties of the resulting electrodes and devices. Preferably, the paste is Pb-free. The present invention provides a silver thick film paste composition that simultaneously provides a Pb-free system with lower firing temperatures while maintaining electrical and mechanical performance.